Motion compensating device for surface supported underwater structures

ABSTRACT

A stable platform for handling small submersibles and other underwater apparatus from the surface employs a self-reeling buoyant winch to isolate the platform from surface motion. A ballasting arrangement is controlled from the surface to recover the platform and its load without platform or vehicle manipulation. The deck recovery boom and winch arrangement permit the platform to be placed on the deck for on-and-off loading.

Unite States atent [191 Egeberg 1 1 MOTION COIVIPENSATING DEVICE FOR SURFACE SUPPORTED UNDERWATER STRUCTURES [75] Inventor: Lansing E. Egeberg, La Jolla, Calif.

[73] Assignee: The United States of America as represented by the Secretary of the Navy, Washington, DC.

[22] Filed: Sept. 17, 1973 [21] Appl. No.: 398,060

[52] U.S. Cl. 114/435, 61/69 R, 114/16 R, 1 14/50 [51 Int. Cl. B63c 7/02 [58] Field of Search.... 114/206 R, 230, 16 E, 16 R, 114/168, 43.5, 50, 51; 9/8 R, 8 P; 61/69 R [56] References Cited UNITED STATES PATENTS 834,647 10/1906 Toomey 61/69 3,093,848 6/1963 Schick 9/8 R 3,111,926 11/1963 Shatto..... 114/206 R 3,295,489 1/1967 BOSsa 114/206 R 3,402,687 9/1968 Tsuji 9/8 R Apr. 30, 1974 10/1970 Toher et al. 114/435 6/1929 Hartman 61/69 R OTHER PUBLICATIONS John D. Isaacs et a1., Deep-Sea Mooring, 1963, Univ. of Calif. Press, Berkeley and Los Angeles, pages 271312.

Primary ExaminerTrygve M. Blix Assistant Examiner-Galen L. Barefoot Attorney, Agent, or FirmRichard S. Sciascia; Ervin F. Johnston; William T. Skeer 5 7 ABSTRACT A stable platform for handling small submersibles and other underwater apparatus from the surface employs a self-reeling buoyant winch to isolate the platform from surface motion. A ballasting arrangement is controlled from the surface to recover the platform and its load without platform or vehicle manipulation. The deck recovery boom and winch arrangement permit the platform to be placed on the deck for on-and-off loading.

10 Claims, 3 Drawing Figures PATEriumao m4 sum 2 UF 2 MOTION COMPENSATING DEVICE FOR SURFACE SUPPORTED UNDERWATER STRUCTURES STATEMENT OF GOVERNMENT INTEREST The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

FIELD OF THE INVENTION This invention pertains to the fields of marine engineering and naval architecture. More particularly, the invention pertains to the field of cargo handling apparatus for surface vessels. In still greater particularity, the invention pertains to an at-sea on-and-off loading arrangement for submarine vehicles and apparatus. By way of further specification, but without limitation thereto, the invention pertains to a stable underwater platform for the handling of small submersible vehicles by a surface ship.

DESCRIPTION OF THE PRIOR ART Launch and retrieval of the smaller variety of submersibles has traditionally been at the surface by some type of vessel with a lifting capacity of relatively modest proportions. In the prior art, conventional cargo handling booms and lifts have traditionally been employed. The problems encountered with this type of equipment fall mainly into two categories: The first of these is the release during launch and the hooking up for recovery of the submersible at the water surface, the second is the control of the submersible while suspended by the lifting of equipment over the side of the parent vessel and the moving of it to its cradle or storage position on the deck of the surface vessel. In nearly all prior art arrangements, swimmers or divers are required to make either the final engagement or disengagement. This restriction has meant that the entire operational deployment of these vehicles as restricted to relatively low sea states and mild temperatures.

Some progress has been made to ameliorate the effects of the sea state on these operations. The use of articulated boom cranes, anti-pendulation devices, quick reeving devices, and constant tension devices have been used in these applications with limited success.

Platforms have also been used for recovery at the surface and in a submerged position, as shown in US. Pat. No. 3,536,023 to Robert A. Toher et al. for Stabilized System for Handling Small Submarines. However, the platforms of the prior art have required either a balancing and control arrangement on the platform itself or a complex above-water control system. Many of these platforms also require the use of divers to operate controls located on the platform itself.

SUMMARY OF THE INVENTION The system of the invention employs a self-reeling, positively-buoyant buoy to isolate a platform from sea state induced motions and a chain ballasting system which permits control of the ascent and descent of the platform from the surface vessel.

STATEMENT OF THE OBJECTS OF THE INVENTION It is accordingly an object of this invention to provide an improved hoisting apparatus for a marine vessel.

A further object of this invention is to provide the recovery apparatus for submarine objects.

Still another object of the present invention is to provide for the surface launch and recovery of submersible vehicles by means of a stabilized self-ballasting platform.

These and other objects of the invention will become more readily apparent from the ensuing specification when taken with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation view of the invention in its operational environment;

FIG. 2 is an end elevation view of the invention shown in its environment; and

FIG. 3 is a force diagram of the systems of the inven tion useful in understanding the operational details of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a stabilized platform indicated generally at 11 includes a horizontal platform 12 and a rectangular support 13 extending above platform I2 and connected thereto. A guideway 14 extends be tween the upper portion of support 13 and platform 12 and provides a guiding runway for a buoyant reeling mechanism indicated generally at 15. A length of flexible cable or other suitable line, indicated at I6, extends downwardly from the underside of platform 12 and supports at its distal end a length of ballast chain 17. A length ofline on cable 18 connects the other end of ballast chain 17 to suitable cable handling mechanism located at the surface.

A flexible cable or other suitable line, indicated at 19, is attached to buoyant reel mechanism 15 and is fed by a suitable roller purchase 20 carried on support 13.

A surface support vessel 21 provides the operation platform from which stabilized platform 11 is controlled. Vessel 21 may be an oceanographic ship, a barge, or other surface vessel as conditions may warrant. As shown, a double drum winch 22 provides winding and storage capacility for cable 18 and a similar double drum winch 23 pays out and reels in flexible cable 19. A state-of-the-art motor, such as fluid motor 24, is connected, via linkages 25 and 26 to a boom 27 which is mounted on the edge of vessel 21. As will be more readily visualized with reference to FIG. 2, boom 27 and motor 24'together wth linkages 25 and 26 are doubled to provide a spaced boom pair connected by a strongback 30 and operate together to provide lifting and deck handling for stabilized platform 11. A suitable platform engagement grapnel or mechanism 28 and sheaves or other reeving purchases 29 are carried on strongback 30 and supported thereby between booms 27. Booms 27 are pivoted at the edge of vessel 21 by means of a suitable pivoting support 31. I

The nature of the invention permits stabilized platform 11 to be handled from either the side or the stern of surface vessel 21. It should also be obvious that boom 27 may operate from a fixed shore installation such as a suitablepier, if desired. 1

Referring to FIG. 2, it may be seen that supports 13 extend vertically from either side of platform 12 and provide an unobstructed working space therebetween.

Vessel 21 is also provided with a deck-mounted sheave 32, or other line handling apparatus, to direct lines 18 to wench 22.

The spacing of booms 27 is such as to allow platform 12 including upright supports 13 to swing therebetween. This critical dimensioning permits booms 27 to be withdrawn to extend over the deck of vessel 21 so as to place stabilized platform 11 in a predetermined location on the deck of vessel 21. This position is illustrated by broken lines in FIG. 1.

As previously seen in FIG. 2, buoyant tension members 15 comprises a relatively large diameter drum 34 secured to a smaller diameter drum 35 and secured to an axle 33. Drum 35 extends on either side of drum 34 and similarly axle 33 extends beyond the outer surface on drum 35. The diameter of drum 34 is chosen such that to the full extent of travel within guide 14 carried by vertical support 13 may be traversed with a single wrap of cable 19 about drum 34. If desired, platform 12 may be relieved to accept drums 34 and 35 so as to permit axle 33 to traverse to maximum range of guide 14. Two lengths of cable 36 are attached to platform 12 and wound on drum 35 to distribute the lifting load supplied by cable 19 to platform 20 without causing twisting or binding of buoyant tension mechanisms 15 within guides 14.

The docking of the submersible vehicle to platform 12 and the launch therefrom is facilitated by conventional structure known in the arts. Accordingly, a further description of this structure is believed unnecessary for the understanding of the invention. However, it should be noted that the type of docking mechanism which is activated by the submersible vehicle itself is preferred in the instant application.

Similarly, the gripping of supports 13 by grapnel means 28 is not shown in detail since a variety of conventional state-of-the-art coupling systems may be used for this purpose. Alternatively, if desired, platform 11 may be simply suspended from sheaves 29 by cable 19 and grapnel means 28 may be dispensed with.

Platform 12, vertical support 13, guides 14, and

' buoyant tension mechanism 15 are all fabricated from conventional materials used in the marine engineering arts. The particular materials are chosen in dependence upon the mechanical stresses anticipated and with a view of the corrosive action of sea water and marine life on such mechanisms. To this end, stainless steel, aluminum, brass, and certain types of water impervious hardwoods have been employed with success in the construction of developmental models of the invention. Choice among these conventional materials, as previously indicated, is based upon the particular application considerations.

In the developmental model, platform 12 has an area of approximately 200 square feet and an in-air weight of 8.000 pounds. Platform 12 has an in-water weight of 2,000 pounds and the buoyant tension mechanisms each have a positive buoyancy of somewhat less than 2,000 pounds. Choices among these parameters will be facilitated by reference to the following mode of operation.

PREFERRED MODE OF OPERATION Referring to FIG. 3, a simplified schematic representation of the forces acting on the system of the invention is shown. Surface vessels 21 is represented by a block, while buoyant tensioning mechanism 15 is shown separated from any guiding structure. Stabilized platform 11, represented by a block, has an in-water mass represented by W1 and is connected to buoyant tensioning mechanism 15 by means of a line exhibiting tension as indicated by T2. Ballast chain 17 is shown as having a weight represented by W2 which is expressed as weight per unit-length. Ballast chain 17 has its distal end connected to surface vessel 21 by means ofline exhibiting a tension represented by T3. Drum 34 is shown as having a radius R1 and drum 35 as having a radius R2.

Assuming for the purpose of illustration, that the cradle is stationary with respect to the bottom and suspended from surface vessel 21, when the tension T1 exceeds product of R1 divided by R2 times the buoyancy B, the buoyant tension mechanism 15 winds downwardly toward platform 12. This winding increases the length of lines between the platform and the surface as the product of R1 divided by R2 times the distance traveled. Similarly, a reduction in the tension will cause buoyant tension mechanism 15 to rise shortening the length of line equal to the product of R1 divided by R2 times the distance traveled. In this manner, buoyant tension mechanism 15 accomodates the vertical motion of surface platform 21 due to sea states and small changes in the tension T1 which result from such sea state activity.

The conditions producing static equilibrium in which the sum of the moments about the center of 15 equals zero and the sum of the forces equal zero are shown in the equations of FIG. 3. That is, EM T,R, T R 0 and EF=T,+B(W,+ W L )=0.

If the weight of the cradle has changed, as in the retrieval or launch of a submersible stabilized platform 11 will move up or down at a distance proportional to the weight per unit length of ballast chain, indicated as W Equations for these changes and W, or T, are AW, AL W and AL, AL /2 (R,/R AL, This movement reestablishes the static equilibrium. From a static point of view, buoyant tension mechanism 15 acts as a constant tension device while ballast chain 17 acts to compensate the system for small changes in platform weight associated with the presence or action absence of the submersible on stabilized platform 11.

In operation, boom 27 is moved from the broken line position, FIG. 1, to transport stabilized platform 11 from its resting position on the deck of surface vessel 21 to a position where the platform is clear of vessel 21. This motion is, of course, effected by the use of motor 24 and linkages 25 and 26. Winch 23 and winches 22 are actuated to lower stabilized platform 1 1 and ballast chain 17 to the illustrated operational position. From this position, the submersible load is either launched or recovered with the stabilization of platform 11 occurring as a result of the operations previously described.

Because of virtual mass of the platform is large in relation to both the buoyant tension mechanism 15 and ballast chain 17, it resists changes in tension T2 and W2 times L2 to a far greater degree than will tension mechanism l5 and ballast chain 17. The result is a highlydamped, self-compensating system which will alternately absorb and release the work imparted to it by its surface platform motion due to the sea state. The result is platform 11 remains at a very nearly constant position relative to the bottom.

Upon recovery, winch 22 is operated to effectively reeve in ballast chain 17 which, from the theoretical standpoint, shortens the length of ballast chain L2 and permits the stabilized platform 11 to rise due to the now-positive buoyancy of the system. Winch 23 is controlled to keep the tension T1 in cable 19 relatively constant. This may be done mechanically or manually, as desired. When the platform 11 is at the surface, vertical supports 13 are engaged by the grapnel mechanism 28 carried on strongback 30 and boom 27 is raised by means of motor 24 working through linkages 25 and 26.

The length of cable 16 connecting stabilized platform 11 to ballast chain 17 permits deck personnel to uncouple ballast chain 17 and attach suitable handling lines for stabilization of the platform as it is moved to its rest position on the vessel 21.

Although conceptually depicted in FIG. 3 as having a single ballast chain 17, the invention may employ two ballast chains connected to either side of platform 12 in a manner shown in FIG. 2. Such an arrangement permits greater flexibility in handling, the use of smaller ballast chain 17, and affords some lateral stability to the system.

The foregoing description taken together with the appended claims constitute a disclosure to enable a person skilled in the naval architecture and marine engineering arts having the benefit of the teachings contained herein to make and use the invention. Further, structure herein described meets the aforesaid objects of invention, and generally constitutes a meritorious advance in the art unobvious to such a skilled worker not having the benefit of these teachings.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings, and, it is therefore understood that within the scope of the disclosed inventive concept, the invention may be practiced otherwise than specifically described.

What is claimed is:

l. A marine launch and recovery system comprising a platform for support of an object to be launched and recovered;

a support frame means attached at its lower end to said platform and extending vertically upward therefrom for support of said platform from above;

buoyant tension mechanism supported for vertical reciprocation within said support frame means;

surface line means attached to said buoyant tension mechanism at its distal end for tethering said platform;

support line means effectively connected between said buoyant tension mechanism and said platform for vertical support of said platform;

a ballast means effectively connected to the underside of said platform for ballasting said platform to a desired buoyancy;

a ballast line means attached to said ballast means for control thereof; and

surface means attached to said surface line means and to said ballast line means for control and support of said platform.

2. A marine launch and recovery system according to claim 1 in which said buoyant tension mechanism includes a first cylindrical drum receiving said surface line means for winding thereabout; and

a second cylindrical drum attached to and concentrically located with respect to said first cylindrical drum receiving said support line means for winding thereabout.

3. A marine launch and recovery system according to claim 2 in which said buoyant tension mechanism further includes an axel concentrically attached to said first and second cylindrical drums and extending outwardly therefrom for cooperative engagement by the aforesaid support frame.

4. A marine launch and recovery system according to claim 3 in which the aforesaid support frame includes guide means to cooperatively receive said axel to direct the vertical movements of said buoyant tension mechanism.

5. A marine launch and recovery system according to claim 2 in which said second cylindrical drum has portions extending on both sides of said first cylindrical drum and the aforesaid support line means includes two lines each wound on a serpate extending portion of said second drum.

6. A marine launch and recovery system according to claim 5 in which said buoyant tension mechanism further includes an axle concentrically attached to said first and second cylindrical drums and extending outwardly therefrom for cooperative engagement by the aforesaid support frame.

7. A marine launch and recovery system according to claim 6 in which the aforesaid support frame includes guide means to cooperatively receive said axel to direct the vertical movements of said buoyant tension mechanism.

8. A marine launch and recovery system according to claim 7 in which said support frame means includes two supports, one located on each side of the aforesaid platform.

9. A marine launch and recovery system according to claim 1 in which said ballast means includes a length of chain.

10. A marine launch and recovery system according to claim 9 in which said length of chain is attached to the platform by a length of cable. 

1. A marine launch and recovery system comprising a platform for support of an object to be launched and recovered; a support frame means attached at its lower end to said platform and extending vertically upward therefrom for support of said platform from above; buoyant tension mechanism supported for vertical reciprocation within said support frame means; surface line means attached to said buoyant tension mechanism at its distal end for tethering said platform; support line means effectively connected between said buoyant tension mechanism and said platform for vertical support of said platform; a ballast means effectively connected to the underside of said platform for ballasting said platform to a desired buoyancy; a ballast line means attached to said ballast means for control thereof; and surface means attached to said surface line means and to said ballast line means for control and support of said platform.
 2. A marine launch and recovery system according to claim 1 in which said buoyant tension mechanism includes a first cylindrical drum receiving said surface line means for winding thereabout; and a second cylindrical drum attached to and concentrically located with respect to said first cylindrical drum receiving said support line means for winding thereabout.
 3. A marine launch and recovery system according to claim 2 in which said buoyant tension mechanism further includes an axel concentrically attached to said first and second cylindrical drums and extending outwardly therefrom for cooperative engagement by the aforesaid support frame.
 4. A marine launch and recovery system according to claim 3 in which the aforesaid support frame includes guide means to cooperatively receive said axel to direct the vertical movements of said buoyant tension mechanism.
 5. A marine launch and recovery system according to claim 2 in which said second cylindrical drum has portions extending on both sides of said first cylindrical drum and the aforesaid support line means includes two lines each wound on a serpate extending portion of said second drum.
 6. A marine launch and recovery system according to claim 5 in which said buoyant tension mechanism further includes an axle concentrically attached to said first and second cylindrical drums and extending outwardly therefrom for cooperative engagement by the aforesaid support frame.
 7. A marine launch and recovery system according to claim 6 in which the aforesaid support frame includes guide means to cooperatively receive said axel to direct the vertical movements of said buoyant tension mechanism.
 8. A marine launch and recovery system according to claim 7 in which said support frame means includes two supports, one located on each side of the aforesaid platform.
 9. A marine launch and recovery system according to claim 1 in which said ballast means includes a length of chain.
 10. A marine launch and recovery system according to claim 9 in which said length of chain is attached to the platform by a length of cable. 